It appears that there is no insulating material between the Aluminum ribs and the Aluminum roof sheet (I can't tell for sure). If not that creates a large thermal "short" allowing direct thermal conduction from inside to outside (heat moves from hot to cold).
Seems to me a thin layer of insulating material (a sheet or tape) between each rib and the skin would minimize the thermal short and help cut down heat loss. Filling the Aluminum channel with form would also help as well as minimize a volume where vapor can condense and the leak out.
I have noticed ice forming on screw heads in the ceiling of our FWC and that got me wondering if the aluminum frame is in thermal contact with the skin. I think it is.
If there is more information on this I am interested in reading about it.
The roof frame is completely covered in a good closed cell tape. It looks like the metal in some pictures. If you look down to the picture with the roof skin you will see the tape on the edge. The insulation that is doubled up in the roof has a combined R value of almost 7. That is more than double of solid insulation.
Edited by marty, 15 November 2013 - 10:48 PM.